Bearing seal for water pump

ABSTRACT

A bearing seal for a water pump of an automobile has rolling elements between an outer ring fixed to a casing and a rotary shaft that is provided with a drive portion at one end and an impeller at the other end. In addition, a seal is formed between the outer ring and the rotary shaft by an annular seal body fixed to each end of the outer ring. The seal body on at least the impeller end of the rotary shaft is made of hydrogenated nitrile rubber, to achieve a seal body that is inexpensive but does not deform, even when used in a high-temperature environment in contact with cooling water in a long time.

BACKGROUND OF THE INVENTION

The present invention relates to a bearing seal for a water pump that issuitable for an application such as a water-cooled engine of anautomobile and, in particular, to a bearing seal that prevents theintrusion of water, water steam, or the like into a bearing thatsupports a rotary shaft of a water pump, and which simultaneouslyprevents any leakage of grease from within the bearing to the outside.

As shown in FIG. 6, a water pump 30 that pressurizes cooling waterhoused in a pump chamber 50 of an engine to cause it to circulate isgenerally configured in such a manner that a rotary shaft 12, on whichan impeller 32 is fixed at one end and a drive means 60 comprising apully 61 and a drive belt 62 are fixed at the another end, is supportedwithin a casing 38 by a plurality set of roller bearings 10 disposedhaving a distance therebetween in the axial direction. The cooling wateris sealed from the exterior by a mechanical seal 40 that is disposedbetween the impeller 32 and the rolling bearings 10. However, since thesliding surface between the inner surface of the mechanical seal 40 andthe rotary shaft 12 is in a water-lubricated state, water steam or thelike will leak therefrom and will enter the roller bearings 10 side fromthe sliding surface if no further contrivance is provided. If steam orthe like enters the interior of the roller bearings 10, it will damagethe roller bearings 10. To prevent the intrusion of water steam or thelike from the impeller 32 side into the roller bearings 10 in such aconfiguration, an annular seal body (not shown) is provided on theimpeller 32 side of the roller bearings 10. Nitrile rubber, which has anexcellent water resistance, or a fluororubber, which has an excellentthermal resistance, is used as the material of this annular seal body.

SUMMARY OF THE INVENTION

Concomitant with recent increases in engine capacities and outputs,temperature conditions for the surrounding of an engine have become moresevere, so that the ambient temperature of such bearings can easilyexceed 110° C.

However, the thermal resistance of nitrile rubber reaches a limit atapproximately 100° C. Thus, if nitrile rubber is used as the material ofa seal body for the bearings 10, thermal deterioration of the seal bodywill result in cracking and a loss of elasticity of lip portionsthereof, so that the sealing properties of the seal body will be lost.

The thermal resistance of fluororubber reaches a limit at a temperatureof at least 200° C., so there would be no problem concerning thermalresistance if fluororubber were used under the above temperatureconditions, but it is extremely expensive.

There is a further problem with both nitrile rubber and fluororubber inthat they will deteriorate and deform if brought into contact with theadditives comprises within cooling water, which would damage the sealingproperties thereof.

An object of the present invention is to solve the above describedproblems and provide a bearing seal device for a water pump which isprovided with a seal body that can be used in a high-temperatureenvironment, does not deform when in contact with cooling water, and isalso inexpensive.

The present invention achieves the above objective by providing abearing seal for a water pump disposed within a casing, wherein thebearing seal comprises:

an outer ring formed within the casing;

a rotary shaft which is equipped with a drive portion at one end portionand an impeller at another end portion, and which is provided in afreely rotatable manner within the outer ring with rolling elementstherebetween; and

a seal body affixed to each end of the outer ring in the axialdirection;

wherein at least the seal body on a side close to the impeller is formedof hydrogenated nitrile rubber.

In this case, hydrogenated nitrile rubber has superior thermal andchemical resistance in comparison with nitrile rubber, and it also has asuperior chemical resistance in comparison with fluororubber. Ifhydrogenated nitrile rubber is used as a seal body in a bearing for awater pump, therefore, the seal body can be expected to exhibitfavorable sealing properties over a long period of time, withoutdeteriorating when used in a high-temperature environment and in contactwith cooling water. Thus there is no intrusion of water steam or thelike into the bearing, and the bearing efficiency thereof does notdeteriorate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view in the axial direction ofessential components of a first embodiment of this invention;

FIG. 2 is a vertical cross-sectional view in the axial direction ofessential components of a second embodiment of this invention;

FIG. 3 is a cross-sectional view of a test apparatus used for testingand comparing the capabilities of seal bodies in accordance with thepresent invention and seal bodies of the prior art;

FIG. 4 is a graph of changes in the hardness of the main lip withrespect to test time;

FIG. 5 is a graph of deterioration in the water resistance of sealbodies with respect to test time; and

FIG. 6 is a vertical cross-sectional view in the axial direction of awater pump to which the bearing seal of the present invention isapplied.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

Embodiments of the bearing seal device of the present invention will bedescribed below with reference to the accompanying drawings.

First Embodiment

An axial cross-sectional view of a bearing seal 400 in accordance with afirst embodiment of this invention is shown in FIG. 1. In this figure,the interior of a bearing 10 is packed with grease or the like, and thebearing 10 itself comprises an outer ring 10 a, a rotary shaft 12 thatforms an inner ring, balls 10 b that are installed between the outerring 10 a and the rotary shaft 12, and a holder 10 c that holds theballs 10 b. The bearing seal 400 also comprises a seal member 15 and aflinger 20. The seal member 15 is disposed within one of sealing grooves10 d that are provided at each end in the axial direction of the outerring 10 a. The seal member 15 comprises a metal core member 15 a and aseal body 15 b, where the seal body 15 b has three lip portions 15 c, 15d, and 15 e, as shown in the lower portion of FIG. 1. The metal coremember 15 a has a cross-section of an inverted L-shape after caulked andis attached to the interior of the sealing groove 10 d of the outer ring10 a by caulking. The seal body 15 b is firmly attached to an outersurface of the metal core member 15 a.

The seal body 15 b is made of hydrogenated nitrile rubber and has abifurcated cross-sectional shape as shown in FIG. 1. A main lip 15 eformed in one part thereof extends obliquely downward to the right inFIG. 1 so as to be formed facing axially outward, and a first sub-lip 15d formed in another part thereof extends obliquely downward to the leftin FIG. 1 so as to be formed facing axially inward. A circularcylindrical second sub-lip 15 c is formed in such a manner as to extendfrom the seal body 15 b at an intermediate position of the metal coremember 15 a toward the right in FIG. 1. It is positioned radiallyoutward from the main lip 15 e and extends outward in the axialdirection.

The flinger 20 is made of stainless steel and is disposed above therotary shaft 12 on the impeller side thereof. The flinger 20 comprises asmall circular cylinder 20 c that engages with and is fixed tightly tothe outer periphery of the rotary shaft 12, a large circular cylinder 20a that encompasses the small circular cylinder 20 c coaxially, and aflange portion 20 b that connects the circular cylinder 20 a and 20 ctogether in the radial direction.

The configuration is such that the second sub-lip 15 c of the seal body15 b is in contact with the outer periphery of the large circularcylinder 20 a of the flinger 20, the main lip 15 e is in contact withthe outer periphery of the small circular cylinder 20 c, and the firstsub-lip 15 d is in contact with the outer peripheral surface of therotary shaft 12, with each contact forming a sealed portion.

The description now turns to the operation of this bearing seal 400. Theconfiguration is such that, when steam or water droplets of the coolingwater are sprayed inward from the outside of the bearing seal 400, theyare intercepted by the outer side surface of the flinger 20 so that thecooling water or the like does not come into direct contact with theseal member 15. This makes it possible to prevent distortion or swellingof the seal member 15 (particularly of the second sub-lip 15 c).

The grease or the like that fills the interior of the bearing 10 issealed in by the first sub-lip 15 d and the main lip 15 e of the sealmember 15, thus preventing leakage of the grease to the outsidetherefrom.

Second Embodiment

A second embodiment of the present invention will now be described. Anaxial cross-sectional view of a bearing seal device 100 in accordancewith this second embodiment is shown in FIG. 2. The second embodimentdiffers from the first embodiment only in the structure of the sealmember 115. The rest of the configuration is the same, so furtherdescription of identical components is omitted herein.

A seal member 115 comprises a metal core member 115 a and a seal body115 b made of hydrogenated nitrile rubber, where the seal body 115 b hasthree lip portions 115 c, 115 d, and 115 e, as shown in the lowerportion of FIG. 2. The metal core member 115 a is an annular plate thatis formed in such a manner that an inner peripheral portion thereof isshifted towards the right in FIG. 2. The seal body 115 b is firmlyattached to an outer surface of the metal core member 115 a and an outeredge of the seal body 115 b is press-fitted into the sealing groove 10d. The shapes of a main lip 115 e, first sub-lip 115 d, and secondsub-lip 115 c of the seal body 115 b are configured in a similar mannerto those of the first embodiment.

Test Samples

Thermal resistance and water resistance tests were performed on bearingsprovided with seal bodies of the configurations shown in FIGS. 1 and 2,using the test apparatus shown in FIG. 3.

The test apparatus of FIG. 3 is configured in such a manner that a testbearing 81 rotated by a drive means 88 is heated by a heater 83 via ahousing 82, and a constant quantity of cooling water is supplied theretoby a constant volume pump 84. It also comprises a thermocouple 86 thatmeasures the temperature of an edge portion of the test bearing 81, anelectrical resistance measurement circuit 87 that measures, by means ofa register 89, the resistance of the bearing shaft 80, and a drivepulley 88 that rotates the bearing shaft 80 at a predeterminedrotational speed. This test apparatus was used to investigate changeswith time in the efficiency of a seal member 85 provided at an endportion of the test bearing 81.

Bearings in which seal bodies 15, 115 of the configurations shown inFIGS. 1 and 2 were of hydrogenated nitrile rubber were used as textsamples of the present invention and prior-art bearings in which sealbodies were of nitrile rubber were used as comparative examples. Theresults were as shown in FIGS. 4 and 5.

FIG. 4 is a graph of changes in the hardness of the main lip(corresponding to the main lip 15 e of FIG. 1) of the seal body withrespect to test time. Hardness was measured as International RubberHardness Degree (IRHD). As shown in this graph (FIG. 4), the bearingsthat were test samples of this invention, in which the seal bodies wereof hydrogenated nitrile rubber, had an elasticity that remained stableover a long period of time, which was 600 hours. In contrast thereto,the prior-art bearings in which the seal bodies were of nitrile rubberdeteriorated in that the hardness of the main lips thereof increasedwith time, cracking and a loss of elasticity caused the seal lips tolose their compliancy, and they became no longer capable of fulfilling asealing function. From these results, it is clear that the test samplesof this invention had less deformation that the comparative examples,and had excellent thermal and chemical resistance properties.

FIG. 5 is a graph representing the deterioration of water resistance inthe seal bodies 15, 115 with respect to time. Note that thisdeterioration of water resistance is expressed as the ratio of thenumber of samples in which efficiency failed due to water leakage, withrespect to the total number of samples.

As shown in this graph (FIG. 5), the bearings that were test samples ofthis invention, in which the seal bodies were of hydrogenated nitrilerubber, had a 50% failure rate after 500 hours had elapsed, whereasvirtually almost all the prior-art bearings in which the seal bodieswere of nitrile rubber had failed after 500 hours had elapsed. Fromthese results, it is clear that the test samples of this invention had afar better water resistance than the comparative examples.

Since the seal body 15, 115 in accordance with this invention is made ofhydrogenated nitrile rubber, it has superlative thermal and chemicalresistance and can exhibit favorable sealing capabilities over a longperiod of time. There is no intrusion of any water steam or the likethat has passed through the mechanical seal from the impeller side, thusensuring stable bearing capabilities.

1. A bearing seal for a water pump disposed within a casing of the waterpump and in contact with additives contained in a cooling watercirculated by the water pump, wherein said bearing seal comprises: anouter ring formed within said casing of the water pump: a rotary shaftwhich is equipped with a drive portion at one end portion and a waterpump impeller at another end portion, and said rotary shaft arrangedfreely rotatably in said outer ring with rolling elements disposedbetween said outer ring and said rotary shaft; and a seal member affixedto said outer ring on a side closer to said water pump impellercomprising a metal core member and a seal body, wherein said metal coremember is disposed on a side of the seal member closer to said driveportion end portion and said seal body is disposed on a side of the sealmember closer to said water pump impeller end portion; a finger isdisposed above said rotary shaft on the impeller side thereof; whereinsaid seal body is formed of hydrogenated nitrile rubber and comprises aplurality of lip portions, only an outer edge of the seal body beingfirmly press-fitted into a sealing groove of said outer ring in directcontact therewith, and said lip portions of the seal body being arrangedin slidable contact with an outer peripheral portion of a rotatingmember or said finger as well as an inner diameter of an inner end ofsaid outer ring being larger than an outer diameter of an outerperiphery of said metal core member and wherein a gap is defined betweensaid inner end of said outer ring and said outer periphery of said metalcore member disposed toward said sealing groove, whereby excellentchemical resistance is maintained over a long period of time by the useof the hydrogenated nitrile rubber.